Rotating media storage devices are an integral part of computers and other devices with needs for large amounts of reliable memory. Rotating media storage devices are inexpensive, relatively easy to manufacture, forgiving where manufacturing flaws are present, and capable of storing large amounts of information in relatively small spaces.
A typical rotating media storage device uses a rotatable storage medium with a head disk assembly and electronics to control operation of the head disk assembly. The head disk assembly can include one or more disks. In a magnetic disk drive, a disk includes a recording surface to receive and store user information. The recording surface can be constructed of a substrate of metal, ceramic, glass or plastic with a thin magnetizable layer on either side of the substrate. Data is transferred to and from the recording surface via a head mounted on an arm of the actuator assembly. Heads can include one or more read and/or write elements, or read/write elements, for reading and/or writing data. Drives can include one or more heads for reading and/or writing. In magnetic disk drives, heads can include a thin film inductive write element and a magneto-resistive (MR) read element.
The hard disk drives are typically calibrated to make them work, or operate more optimally. Examples of calibrations results include Servo bias, Kt/J, Runout harmonics, Position Error Signal (PES) calibration, write current and read head bias. The calibration values can vary over time, temperature, and voltage so in many cases calibration is done after each power up. For mobile devices this can be a problem because periodic calibrations can consume battery power and/or delay work for a user's I/O request.